Judaism, Islam and Christianity all branch from the same tree. You can call it a Macintosh, a red delicious or a granny smith, but they are all apples that grew on a apple tree. Are you denying that these religions all came from a common source??

No, but I'm saying that they are completely different. Judaism and Christianity are the same religion. One is the history of the other. Islam is a split of VERY EARLY Judaism. It has different prophets, different Dogmas, It's a completely different religion. Most would argue that they even worship a perversion of the Jewish/Christian God. If it was the same God, who is unchanging and just, then there wouldn't be that difference because that would mean he lied to one which would mean he wasn't just or unchanging.

Because Islam has different prophets and views on salvation/heaven/hell/ETC, it would make no sense to say that the cross commemorates an Islamic attack. To a Muslim I'm not more an infidel then you are. If anything, I think they should keep the cross because of the hope that it represents in this specific scenario.